A high IIP2 doubly balanced sub-harmonic mixer in 0.25μm CMOS for 5-GHz ISM band direct conversion receiver

This paper presents a new low power and high IIP2 0.25- m CMOS doubly balanced sub-harmonic mixer for 5 GHz; Industrial Scientific Medical (ISM) band direct conversion - zero IF receiver. Using 1/2X LO frequency generation scheme the sub-harmonic mixer, designed and fabricated, overcomes LO self-mixing problem common in conventional direct conversion receivers (DCR). Measurement shows the sub-harmonic mixer is able to achieve voltage conversion gain of 8.2 dB, input compression, P-1dB of -8 dBm and IIP3 of -2.5 dBm while consuming only 1.35 mA of DC current. Measured results correlate well with simulated results where with 1% g(m) mismatch, 0.5% load mismatch and 20 LO phase error the mixer is able to achieve high IIP2 Of 55.3 dBm, IIP3 of -6.5 dBm, and voltage conversion gain of 8 dB. The proposed mixer takes up less than 1mm(2) of silicon real estate including test die pads.